AaaaaAAaaaAAAaaAAAAaAAAAA!!! -- A Reckless Disregard for Gravity: Fun, arcadey base jumping. Cheap and it has a lot of replay value. Check out vids on youtube to really understand what the game is about.

Braid: Platformer that messes with time and motion ingeniously. It's mostly a puzzle game that uses the best concepts from Prince of Persia and Viewtiful Joe and runs away with them. It also does its' own thing and succeeds.

Trine: I'm not good with describing this one. It's another platformer, it has fine level design and requires you to be able to switch to the appropriate character while playing. The puzzles and levels become much more satisfying as you continue through the series. The story starts of with a few lol's that basically have you thinking "idiots".

Portal: Yea, I like puzzle games on the pc. Sue me. use portals to make it out of the maze. You are the maze rat with a portal gun, you gets no cake.

Most of these games have demos. Just install Steam and search for demo's to see what you can handle or to try out games with similar requirements that may not have a demo.

Ya know, i played Sins, and i REALLY don't get what all the hype is about. I think my biggest problem was that, atleast at a high resolution, you had a choice, either play at a playable zoom level, in which case you couldn't see your ships for jack (they were little just little, or medium flying blocks of your color), or zoom in enough to enjoy the fairly detailed art work, and not be able to see the actual battlefield!

Well a really good game that is a sleeper hit is Cryostasis. Its really weird. You live near the north pole I think and you are dog sledding. And what happens is the ice starts shifting and breaking scattering your dogs you go look for them and fall into a frozen ship. The theme it plays on are life/death/warmth/past/present. Its a crazy awesome game.

Also Torchlight is pretty much Diablo. Pick that up and you'll have a blast if you like Diablo.